Scala Solution to Top Coder problem: http://community.topcoder.com/stat?c=problem_statement&pm=4670&rd=8006 #Learning Scala

ListerningIn.scala

import scala.collection.immutable.StringOps

// Solution to Top Coder problem: http://community.topcoder.com/stat?c=problem_statement&pm=4670&rd=8006
object ListeningIn {
  def probableMatch(typed:String , phrase:String ): String = {
  // recursively consumes both char sequences finding matches. Accumulates the elements in phraseSeq that do not match typeSeq
  // not tail rec
    def matcher(typeSeq:Seq[Char], phraseSeq:Seq[Char]): Option[Seq[Char]] = (typeSeq, phraseSeq) match {
      case (Seq(), Seq()) => Some("")
      case (Seq(), Seq(xs@_*)) => Some(xs)
      case (Seq(_*), Seq()) => None
      case (ts@Seq(x, xs@_*), ps@Seq(y, ys@_*)) =>
        if (ts.length > ps.length) None
        else if (x!=y) matcher(ts,ys).map(x=> y +:x) else matcher(xs,ys)
      }
    matcher(typed, phrase) match {
      case Some(chars) => chars.mkString
      case None => "UNMATCHED"
    }
  }
  probableMatch("port to me","teleport to me")  //> res0: String = tele
  probableMatch("back  to base","back to base") //> res1: String = UNMATCHED
}